1. Which relation holds true for equilibrium constants Kp and Kc?
- A. Kp = Kc (RT)^Δn
- B. Kc = Kp (RT)^Δn
- C. Kp = Kc / (RT)^Δn
- D. Kp = Kc + RT
Answer: A. Kp = Kc (RT)^Δn
Explanation: Kp and Kc are related by Kp = Kc (RT)^Δn, where Δn is the difference in moles of gaseous products and reactants.
2. According to Bronsted-Lowry concept, an acid is a substance which:
- A. Donates a proton (H⁺)
- B. Accepts a proton (H⁺)
- C. Accepts an electron pair
- D. Donates an OH⁻ ion
Answer: A. Donates a proton (H⁺)
Explanation: Bronsted-Lowry theory defines an acid as a proton donor and a base as a proton acceptor.
3. What is the conjugate base of H₂SO₄?
- A. HSO₄⁻
- B. SO₄²⁻
- C. H₃O⁺
- D. SO₃
Answer: A. HSO₄⁻
Explanation: Removing one proton (H⁺) from H₂SO₄ yields its conjugate base, HSO₄⁻.
4. Which of the following acts as a Lewis acid?
- A. BF₃
- B. NH₃
- C. H₂O
- D. Cl⁻
Answer: A. BF₃
Explanation: BF₃ has an incomplete octet on boron, making it an electron pair acceptor (Lewis acid).
5. The pH of a neutral aqueous solution at 25 °C (298 K) is:
Answer: A. 7
Explanation: At 298 K, [H⁺] = [OH⁻] = 10⁻⁷ M, so pH = -log(10⁻⁷) = 7.
6. According to Le Chatelier's principle, adding an inert gas at constant volume to a dynamic equilibrium system will:
- A. Have no effect on equilibrium
- B. Shift equilibrium forward
- C. Shift equilibrium backward
- D. Double the reaction rate
Answer: A. Have no effect on equilibrium
Explanation: Adding inert gas at constant volume does not change the partial pressures or concentrations of the reacting species.
7. The ionic product of pure water (Kw) at 298 K is:
- A. 1.0 × 10⁻¹⁴ M²
- B. 1.0 × 10⁻⁷ M²
- C. 1.0 × 10⁻¹⁰ M²
- D. 1.0 × 10⁻¹ M²
Answer: A. 1.0 × 10⁻¹⁴ M²
Explanation: Kw = [H⁺][OH⁻] = (10⁻⁷)(10⁻⁷) = 1.0 × 10⁻¹⁴ M² at 25 °C.
8. A buffer solution is a solution that resists changes in:
- A. pH value
- B. Temperature
- C. Volume
- D. Pressure
Answer: A. pH value
Explanation: Buffer solutions maintain a nearly constant pH upon the addition of small amounts of acid or base.
9. Which of the following forms an acidic buffer solution?
- A. CH₃COOH + CH₃COONa
- B. NH₄OH + NH₄Cl
- C. HCl + NaCl
- D. NaOH + NaCl
Answer: A. CH₃COOH + CH₃COONa
Explanation: An acidic buffer contains a weak acid (CH₃COOH) and its salt with a strong base (CH₃COONa).
10. If reaction quotient Q < Kc, the reaction will proceed in:
- A. Forward direction
- B. Backward direction
- C. Reverse direction only
- D. Neither direction (at equilibrium)
Answer: A. Forward direction
Explanation: When Q < Kc, reactants convert to products to reach equilibrium, shifting the reaction forward.
11. What is the expression for solubility product (Ksp) of AgCl?
- A. [Ag⁺][Cl⁻]
- B. [Ag⁺] / [Cl⁻]
- C. [Ag⁺]²[Cl⁻]
- D. [Ag⁺][Cl⁻]²
Answer: A. [Ag⁺][Cl⁻]
Explanation: For AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq), the solubility product constant Ksp = [Ag⁺][Cl⁻].
12. For an exothermic reaction, increasing temperature shifts equilibrium to the:
- A. Left (Backward)
- B. Right (Forward)
- C. Remains unchanged
- D. Complete conversion
Answer: A. Left (Backward)
Explanation: Heat is a product in exothermic reactions; adding heat causes the equilibrium to shift left to absorb excess energy.
13. The pH of 0.01 M HCl solution is:
Answer: A. 2
Explanation: Strong acid HCl fully dissociates: [H⁺] = 0.01 M = 10⁻² M. Thus, pH = -log(10⁻²) = 2.
14. Common ion effect causes the degree of dissociation of a weak electrolyte to:
- A. Decrease
- B. Increase
- C. Remain constant
- D. Become zero completely
Answer: A. Decrease
Explanation: Adding a strong electrolyte containing a common ion shifts equilibrium backward, suppressing ionization of the weak electrolyte.
15. An aqueous solution of Sodium Acetate (CH₃COONa) is:
- A. Basic
- B. Acidic
- C. Neutral
- D. Amphoteric
Answer: A. Basic
Explanation: CH₃COONa is a salt of a weak acid and strong base; anion hydrolysis yields excess OH⁻ ions (pH > 7).
16. The units of Kc for the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g) are:
- A. L² mol⁻²
- B. mol L⁻¹
- C. mol² L⁻²
- D. Dimensionless
Answer: A. L² mol⁻²
Explanation: Unit = (mol L⁻¹)^Δn = (mol L⁻¹)^(2-4) = (mol L⁻¹)⁻² = L² mol⁻².
17. Which of the following is amphoteric in nature?
- A. H₂O
- B. HCl
- C. NaOH
- D. NH₄⁺
Answer: A. H₂O
Explanation: Water can donate a proton to form OH⁻ (acting as an acid) or accept a proton to form H₃O⁺ (acting as a base).
18. Salt hydrolysis of a strong acid and strong base salt (e.g., NaCl) produces a solution with pH:
- A. Equal to 7
- B. Greater than 7
- C. Less than 7
- D. Equal to 0
Answer: A. Equal to 7
Explanation: Neither cation nor anion hydrolyzes in water for a salt of a strong acid and strong base, keeping pH neutral at 7.
19. If the solubility of AB₂ salt is 'S' mol/L, its solubility product Ksp is:
- A. 4S³
- B. S²
- C. 27S⁴
- D. 2S²
Answer: A. 4S³
Explanation: AB₂(s) ⇌ A²⁺ + 2B⁻. Ksp = [A²⁺][B⁻]² = (S)(2S)² = 4S³.
20. In Haber's process (N₂ + 3H₂ ⇌ 2NH₃ + heat), high yield of ammonia is favored by:
- A. High pressure and low temperature
- B. Low pressure and high temperature
- C. Low pressure and low temperature
- D. High pressure and high temperature
Answer: A. High pressure and low temperature
Explanation: High pressure shifts equilibrium toward fewer gas moles (NH₃), and low temperature favors the exothermic reaction.
21. The relationship between pH and pOH at 298 K is:
- A. pH + pOH = 14
- B. pH - pOH = 14
- C. pH × pOH = 14
- D. pH / pOH = 14
Answer: A. pH + pOH = 14
Explanation: Taking -log on both sides of Kw = [H⁺][OH⁻] = 10⁻¹⁴ gives pH + pOH = 14.
22. What happens to the pH of water when temperature is increased?
- A. Decreases
- B. Increases
- C. Remains constant
- D. Becomes 14
Answer: A. Decreases
Explanation: Dissociation of water is endothermic, so Kw increases with temperature, raising [H⁺] and lowering pH (though water remains neutral).
23. Henderson-Hasselbalch equation for an acidic buffer is:
- A. pH = pKa + log([Salt] / [Acid])
- B. pH = pKa - log([Salt] / [Acid])
- C. pH = pKb + log([Salt] / [Base])
- D. pH = pKa + log([Acid] / [Salt])
Answer: A. pH = pKa + log([Salt] / [Acid])
Explanation: The Henderson-Hasselbalch equation relates pH to pKa and logarithmic ratio of conjugate base to acid.
24. Catalyst added to a reversible reaction at equilibrium:
- A. Increases rates of both forward and backward reactions equally
- B. Increases only forward reaction rate
- C. Shifts equilibrium toward products
- D. Changes equilibrium constant value
Answer: A. Increases rates of both forward and backward reactions equally
Explanation: A catalyst lowers activation energy for both directions equally without shifting equilibrium position or altering K.
25. Precipitation of a salt takes place when ionic product (Qsp) is:
- A. Greater than solubility product (Ksp)
- B. Less than solubility product (Ksp)
- C. Equal to solubility product (Ksp)
- D. Zero
Answer: A. Greater than solubility product (Ksp)
Explanation: When ionic product exceeds Ksp, the solution becomes supersaturated and excess solute precipitates out.
26. Which of the following is a strong electrolyte?
- A. NaCl
- B. CH₃COOH
- C. NH₄OH
- D. H₂CO₃
Answer: A. NaCl
Explanation: Sodium chloride completely dissociates into Na⁺ and Cl⁻ ions in aqueous solution.
27. Ostwald's Dilution Law is applicable to:
- A. Weak electrolytes only
- B. Strong electrolytes only
- C. Non-electrolytes only
- D. Both strong and weak electrolytes
Answer: A. Weak electrolytes only
Explanation: Ostwald's law applies to weak electrolytes where partial dissociation equilibrium is established.
28. The conjugate acid of NH₃ is:
- A. NH₄⁺
- B. NH₂⁻
- C. N³⁻
- D. NH₄OH
Answer: A. NH₄⁺
Explanation: Addition of a proton (H⁺) to NH₃ gives its conjugate acid NH₄⁺.
29. The value of equilibrium constant for a reaction depends on:
- A. Temperature
- B. Initial concentrations
- C. Pressure
- D. Presence of catalyst
Answer: A. Temperature
Explanation: For a given chemical reaction, the equilibrium constant K is a constant that changes only with temperature.
30. An aqueous solution of Ammonium Chloride (NH₄Cl) is acidic because of:
- A. Cationic hydrolysis
- B. Anionic hydrolysis
- C. Both cationic and anionic hydrolysis
- D. No hydrolysis
Answer: A. Cationic hydrolysis
Explanation: NH₄⁺ from weak base hydrolyzes with water to release H⁺ ions, making the solution acidic (pH < 7).
